Big Idea 16: Heredity and
Reproduction
Description
A. Reproduction is characteristic of living things and
is essential for the survival of species.
B. Genetic information is passed from generation to
generation by DNA; DNA controls the traits of an
organism.
C. Changes in the DNA of an organism can cause
changes in traits, and manipulation of DNA in
organisms has led to genetically modified organisms.
Benchmark Number & Descriptor
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SC.7.L.16.1
Understand and explain that every organism requires a set of
instructions that specifies its traits, that this hereditary information
(DNA) contains genes located in the chromosomes of each cell, and
that heredity is the passage of these instructions from one generation
to another.
SC.7.L.16.2
Determine the probabilities for genotype and phenotype
combinations using Punnett Squares and pedigrees.
SC.7.L.16.3
Compare and contrast the general processes of sexual reproduction
requiring meiosis and asexual reproduction requiring mitosis.
SC.7.L.16.4
Recognize and explore the impact of biotechnology (cloning, genetic
engineering, artificial selection) on the individual, society and the
environment.
WHO ARE YOU?
DNA
• DNA =
Deoxyribonucleic Acid
• Traits which are
passed from parents
to offspring are carried
in DNA.
• DNA is a blueprint for
the cells in an
organism.
• Without DNA, an
organisms traits would
never form.
DIRECTIONS
GENES
• Pieces of DNA
• Carry traits
•
Characteristics
• Help pass traits from parent
to offspring
– You inherit your genes.
• Offspring receive only some
genes from parents.
• Genes combine differently,
so you look different.
CHROMOSOMES
• Genes are located on
chromosomes.
– Thousands of genes can be
found on a single
chromosome.
• Chromosomes are found in
the nucleus of the cells.
• Each type of organism
contains a set number of
chromosomes.
– Humans = 23 Pairs
PUTTING IT
ALL
TOGETHER
KNOWLEDGE CHECK
1. What does DNA stand for?
2. Where is DNA located?
3. Why is DNA important?
KNOWLEDGE CHECK
1. What does DNA stand for?
Deoxyribonucleic Acid
2. Where is DNA located? DNA is
located on genes which are carried by
chromosomes.
3. Why is DNA important? It’s the
blueprint for how organisms are
made.
WHY DON’T WE
LOOK ALIKE?
What is Heredity?
• Heredity is the passing on
of characteristics (traits)
from parents to offspring.
• Genetics is the study of
heredity.
Gregor Mendel
• WHO:
– Austrian monk
• WHAT:
– Worked with pea plants and discovered how traits get
passed from generation to generation
• WHEN:
– Around 1856
PASSING OF TRAITS
• Each gene contains 2 ALLELES
– 1 allele from mom
– 1 allele from dad
• Individual alleles are represented by an upper or
lowercase letter.
• Some alleles are dominant, and others are
recessive.
BLUE = allele
RED = allele
together = gene
TRAITS
TYPES OF TRAITS
LETTER COMBINATIONS
• The trait that is observed in
the offspring is the
DOMINANT TRAIT
(uppercase).
• Heterozygous - if the
two alleles for a trait
are different (Aa)
• The trait that disappears in
the offspring is the
RECESSIVE TRAIT
(lowercase).
• Homozygous - if the two
alleles for a trait are
the same (AA or aa)
–
–
It only takes one dominant allele for
that trait to be shown.
It takes 2 recessive alleles for that
trait to be shown.
– Also referred to as a
hybrid combination
– Also referred to as a
purebred combination
TRAITS
GENOTYPE
• Refers to the letter (allele)
combination
– TT, Tt. tt
• If a capital letter is present in
the letter pair, the dominant
trait will be expressed in that
organism.
• If 2 lower case letters are
paired, the recessive trait will
be expressed in that organism.
PHENOTYPE
• Refers to the physical
characteristic being
expressed
• Uses words/phrases to
describe not letters
• Examples:
– tall, short
– white, black
PUNNETT SQUARES
•
•
Tool used to determine
characteristics of offspring
Each box represents the
probability of an offspring
receiving a trait.
– Example:
• Top outside (Tt) is a
gene passed on by the
father
• Left outside (tt) is a
gene passed on by the
mother.
• 4 middle boxes are
possible gene
combinations an
offspring may receive.
T
T
t
Tt
Tt
t
Tt
Tt
T = Tall
t = Short
All offsprings will be tall (all
boxes contain the dominant
trait for tallness).
PUNNETT SQUARES
• Short hair (L) is
dominant to long
• Punnett Square:
hair (l) in mice.
L
l
What is the
Ll
ll
genotype and
l
phenotype ratio of a
l
Ll
ll
heterozygous shorthaired mouse
• Genotype ratio: ½ Ll:
crossed with a long½ ll
haired mouse?
• Phenotype ratio: ½
short hair: ½ long hair
PEDIGREE
• A chart used to trace
traits throughout a
family
• Parts of the chart
– Circle = females
– Squares = males
– Half-filled in/Dotted =
carrier
• Have the gene but do
not show signs of it
– Filled-in = affected
• Have both the gene
and symptoms of that
trait
KNOWLEDGE CHECK
1. What do we call the
trait that is
observed?
2. What case (upper or
lower) is it written
in?
3. What about the one
that disappears?
4. What case is it
written in?
• Trait Tall = Aa
• Trait short = aa
• Aa x aa
5. Complete the Punnett
Square.
____
____
____
____
KNOWLEDGE CHECK
1. What do we call the
trait that is
observed?
Dominant
2. What case (upper or
lower) is it written
in? Upper
3. What about the one
that disappears?
Recessive
4. What case is it
written in? Lower
• Trait Tall = Aa
• Trait short = aa
• Aa x aa
5. Complete the Punnett
Square.
__A_ __a_
_a__ Aa
aa
_a__ Aa
aa
HOW DO WE GET
ALL THIS STUFF?
REPRODUCTION
SEXUAL
ASEXUAL
• Primary method of
reproduction for the vast
majority of visible organisms,
including almost all animals
and plants
• Characterized by two
processes:
– meiosis, halving of the
number of chromosomes
– fertilization, combination of
two gametes and the
restoration of the original
number of chromosomes
• Results in increasing genetic
diversity of the offspring.
• A form of reproduction
which does not involve
meiosis or fertilization
• Asexual reproduction = one
parent.
• The primary form of
reproduction for singlecelled organisms such as
archaea, bacteria, and
protists
• Mitosis is the main way of
reproduction.
REPRODUCTION
ASEXUAL
• MITOSIS
– All forms of asexual
reproduction utilize the
process of mitosis.
– Begins with one replication
(copying of the chromosome
material) and one division of
the chromosome material
– This results is 2 daughter cells
being produced with the same
number of and identical
chromosomes as in the parent
cell.
Asexual reproduction in
liverworts: a caducuous
phylloid germinating
Mitosis
•
•
•
Interphase
– Normal functions
– Upon trigger,
chromosomes & centrioles
duplicate.
Prophase
– Early: nuclear envelope
degrades; chromosomes
start to condense.
– Late: chromosomes
thicken; spindle forms
between centrioles
Metaphase
– Spindle fibers attach to
kinetochores.
– Chromosomes line up at
cell equator.
sdst.org/shs/apbio/... /mitosis powerpoint.ppt
Mitosis
• Anaphase
– Chromatids separate at
centromeres
– Chromosomes move to
poles.
• Telophase
– Nuclear envelope
reforms in each of two
daughter cells.
– Cytokinesis separates
two new cells.
• Interphase
– Daughter cells are
genetically identical to
each other and the
parent cell but smaller.
sdst.org/shs/apbio/... /mitosis powerpoint.ppt
REPRODUCTION
SEXUAL
• MEIOSIS
– Process produces the sex
cells
• Contain ½ the chromosomes
as the parent
– Since ½ male chromosomes
and ½ female chromosomes
combine = genetic variety
Hoverflies mating in midair
flight.
MEIOSIS
•
•
•
•
•
Prophase I: the chromosomes
condense and homologous
chromosomes pair up to form
tetrads.
Metaphase I: the tetrads are
all arranged at the metaphase
plate.
Anaphase I: the homologous
chromosomes separate and
are pulled toward opposite
poles.
Telophase I: movement of
homologous chromosomes
continues until there is a
haploid set at each pole.
Cytokinesis : by the same
mechanisms as mitosis
usually occurs simultaneously
•
•
•
•
Prophase 2: spindle reforms
and chromosomes move
toward the metaphase plate.
Metaphase 2: sister
chromatids lined up on the
metaphase plate.
Anaphase 2: sister chromatids
are separated and pulled
toward opposite poles of the
cell.
Telophase 2 and
Cytokinesis: nuclei form at
either pole, and each cell is
finally divided into two identical
daughter cells.
MEIOSIS
Mitosis vs. Meiosis
REPRODUCTION
SEXUAL
• EXAMPLES:
– Sexual Reproduction
• DNA from 2 individuals merge
to form one.
• Animals, plants
– Fertilization
• Pollen is delivered to female
part of plant.
• Flowering plants
ASEXUAL
• EXAMPLES:
– Fragmentation/Regeneration
• Body of parent breaks and
produces offspring.
• Fungi, moss, sea stars,
planarian
– Budding
• Offspring grows out of parent.
• Yeast, hydras
KNOWLEDGE CHECK
1. Label each of the following as either Asexual or
Sexual reproduction:
•
•
•
•
•
•
•
•
•
•
Spores budding
Nearly all organisms reproduce this way
Mitosis
Meiosis
Starfish is cut in half; both halves grow into a
whole starfish.
One parent needed
Not identical to parents
Two parents needed
Identical to parent
Sperm and eggs
KNOWLEDGE CHECK
ASEXUAL
• Spores budding
• Mitosis
• Starfish is cut in half; both
halves grow into a whole
starfish.
• Identical to parent
• One parent needed
SEXUAL
•
•
•
•
•
Not identical to parents
Two parents needed
Sperm and eggs
Meiosis
Nearly all organisms
reproduce this way.
SHOULD WE MESS
WITH MOTHER
NATURE?
MAKING IT JUST RIGHT
SELECTIVE
BREEDING
HYBRIDIZATION
• The process of using
specific plants or animals
with specific traits to
reproduce offspring with
those traits
• These breeded
plants/animals can be:
• The process of crossing to
plants/animals with different
variations of the same trait
• The resulting offspring is
created to have the best
traits of the parents.
• Examples:
– Larger in size
– Provide more food
– Resistant to disease
– Corn: farmers each year try to
grow corn that are disease
free and higher quality.
– Animals: if 2 different species
are bred, a stronger but sterile
species may be produced
MAKING IT JUST
RIGHT
• INBREEDING
• Involves using two plants/animals that have the same or
similar genes.
• The offspring produced will be purebred.
• If purebreds are created, specific genes can be passed along.
• Inbreeding, though, can cause a population to die.
– Since they are genetically similar, if one animal/plant
comes down with a disease, the entire population may
have it.
BREEDING EXAMPLES
Due to inbreeding, all
cheetahs are closely
related.
Miniature Horse
was specifically
bred small to work
in mines.
Disease
resistance,
greater
nutritional value
Mule combines the
best traits of a horse
and a donkey.
GENETIC ENGINEERING
• Processes in which genes with specific DNA
strands are removed and transferred into another
organism.
– This process is much faster then altering organisms
through breeding techniques.
• Genetic engineering is used in biotechnology,
medicine, and cloning.
GENETIC ENGINEERING
BIOTECHNOLOGY
• Involves growing cells for
industrial purposes
• Agriculture:
– Many plants and crops are
susceptible to disease.
– Scientists have been able to
isolate fighting genes and
insert them into plants/crops
for better survival rates.
GENETIC MODIFICATION
• Genetic engineering produces
a lot of strong feelings among
people.
• PROS:
– Crops and farm animals may be
produced to better tolerate
drought, disease, and infestations,
therefore increasing the food
production around the world.
• CONS:
– Many people are concerned
about mixing genetic material with
different species.
– Once in the wild, the effects of
changes are out of the scientists
hands.
GENETIC ENGINEERING
MEDICINES
• Insulin has been able to be
created through Genetic
engineering.
– Insulin was once made from
animals, but people were allergic
to it. Now it is created from
bacteria with no allergies and is
less expensive.
• Vaccines have been able to be
produced through Genetic
engineering.
– Vaccines such as Hepatitis B are
now less expensive to produce
and can be made in mass
production.
CLONING
• Clones are living things that
have exactly the same
genes.
• Agriculture has done this
forever:
– Taking clippings of plants and
replanting them
– The cuttings grow into new
and identical plants.
• Humans and animals,
however, become more
controversial:
– Is it ok to clone spare body
parts?
GENETIC ENGINEERING
GENE THERAPY
• Faulty genes inside a
human bodies can be
replaced with normal,
healthy ones
• Unfortunately, most cells in
our body only live for a
short period of time.
– The new cells with the new
genes can function for a short
period of time.
WHAT WOULD YOU
DO?
• The more we know about DNA
and genes, the more we may
be able to predict our future.
• People today can be screened
for certain genetic conditions.
• For example
– If a person is found to be a
carrier of a specific gene
defect, he/she will need to
make a choice if he/she are to
have kids.
– Perhaps you carry a gene for
cancer which may or may not
turn on. What would you do?
KNOWLEDGE CHECK
1. Name three types of breeding and a
reason why they are used.
2. What is Genetic engineering?
3. Why is Genetic engineering supported
by some yet forbidden by others?
KNOWLEDGE CHECK
1. Name three types of breeding and a reason why they are
used. Selective breeding, hybridization, inbreeding. All 3 can
be used to make specific higher yielding crops. Crops less
vulnerable to disease and animals for specified jobs
2. What is Genetic engineering? Processes in which genes with
specific DNA strands are removed and transferred into
another organism.
3. Why is Genetic engineering supported by some yet forbidden
by others? Supported = create medicines and cells for
people to survive
Forbidden = Messing with mother nature. Do not
have control if changes were to get into the wild